Apparatus for making rotors for induction motors



Feb. 10, 1953 E. c. HOPKINS 2,627,765

APPARATUS FOR MAKING ROTORS FOR INDUCTION MOTORS Filed Jan. 12, 1951 I 3 Sheets-Sheet l E. C. HOPKIN 8 Feb. 10, 1953 APPARATUS FOR MAKING ROTORS FOR INDUCTION MOTORS Filed. Jan. 12, 1951 3 Sheets-Sheet 2 1520822308 E'Efian Gfiaflias Ho APPARATUS FOR MAKING ROTORS FOR INDUCTION MOTORS Filed Jan. 12, 1951 Feb. 10, 1953 I E. c. HOPKINS 3 Sheets-Sheet 3 Patented Feb. 10, 1953 APPARATUS FOR MAKING ROTORS FOR INDUCTION MOTORS Ethan Charles Hopkins, Arlington, Mass.

Application January 12, 1951, Serial No. 205,625

6 Claims.

This invention relates to the manufacture of rotors of the squirrel cage type for use in small alternating current induction motors.

Such rotors commonly comprise a core member of iron or other material having suitable magnetic characteristics, at each end of which is an end member or head of copper or some other nonmagnetic electrically conductive material, said head being connected by conductor bars also of copper.

It has heretofore been proposed to make rotors of the above type in which the core is composed of compressed and sintered iron powder, and the end members and conducting bars are composed of compressed and sintered copper powder.

One object of the invention is to provide a novel method of and loading mechanism for depositing the iron and copper powder into a mold in which such powder is compressed for shaping into the required form for the rotor.

A further object of the invention is to provide a loading mechanism by which the copper powder can be deposited in the mold in such a way as to make a rotor having conductor bars which are parallel to the rotor axis or which have an inclined position relative thereto, or in which such conductor bars have a curved or angular shape.

In the drawings Fig. l is a vertical sectional view through a loading device embodying the invention.

Figs. 2, 3, 4, and 5 show different steps in the operation of depositing the iron and copper powder into the mold and then compressing said deposited powder into the form of the rotor.

Fig. 6 is an end view of a rotor embodying the invention.

Fig. 7 is a side view of Fig. 6.

Fig. 8 is a view similar to Fig. '7 but showing a rotor having angular conductor bars.

Fig. 9 is a longitudinal sectional view through a rotor embodying the invention.

Fig. 10 is a section on the line Ill-Iii, Fig. 9.

Fig. 11 is an end view.

Fig. 12 is a side view of a rotor embodying the invention and provided with fan blades at its ends.

Fig. 13 is an enlarged section on the line i3--l 3, Fig. 1.

Fig. 14 is a fragmentary side view showing the means for operating the measuring unit by which measured quantities of iron powder are deposited in the mold.

Fig. 15 is an enlarged section on the line 15-45,

Fig. 1.

Fig. 16 is a fragmentary side view showing the means for operating the measuring unit by which measured quantities of copper powder are delivered to the mold.

Fig. 17 is a side view of a rotor embodying the invention with a portion broken out.

Fig. 18 shows a cam element which may be used to make a rotor having angular conductor bars.

Referring now to Figs. 9 and 10, which are sectional views of a rotor made in accordance with my invention, l designates the iron core member and 2 indicates the two end or head members at the ends of the rotor, said end or head members being connected by the conductor bars 3. The

"' end or head members 2 and the conductor bars 3 are made of copper.

In the construction shown the end members are in the form of rings through which project hub portions 4 of the core I.

The core member I is made of compressed and sintered iron powder, and both the head members 2 and the conductor bars 3 are made of compressed and sintered copper powder.

The compressing of the iron and copper powder to form the rotor is accomplished in a mold cavity 5 in a die block 6, said mold cavity having a diameter corresponding to that of the completed rotor.

The mold cavity extends completely through the die block from the top to the bottom thereof and the bottom of said cavity is closed by a punch element 1 through which extends a shaft 8 corresponding to the shaft 9 of the completed rotor. The punch 1 is shown in Fig. 1 as having a recess ID in its upper face by which the hub portion 4 of the rotor is formed when the metal powder in the cavity is compressed.

The powdered iron for forming the core I of the rotor is delivered to the mold cavity through an open ended tube II which is located axially of the cavity and extends to the punch L The powdered copper is delivered to the mold cavity through a plurality of small tubes [2 which are also open at their lower ends and which are located in a circle surrounding the tube ll. Said tubes 12 have the relative position in the mold cavity that the conductor bars 3 are to have in the completed rotor.

Means presently to be described are employed to deliver measured quantities of iron powder to the tube II and measured quantities of copper powder to the tubes l2. These tubes II and I2 are mounted so that they can be moved vertically, and after they have received their measured quantities of powdered metal they are raised,

thereby allowing the powdered metal therein to flow out of the open ends thereof into the mold cavity.

In the operation of filling the mold cavity with the powdered iron and powdered copper, the tube I I is positioned as shown in Fig. 1 with its lower end resting against the punch i, and the tubes I2 are positioned within the mold cavity with their lower-ends spaced slightly above the end of the punch i.

A measured quantity of iron powder is delivered to the tube I I, some of this powder passing through the open end of the tube and filling the recess ID as shown in Fig. 1. Measured quantitles of copper powder are also delivered tothe tubes l2 and such copper powder will flow through the open end of the tubes and will fill the space around the lower end of the tube II thereby forming a ring I i of copper powder in the bottom of the mold cavity.

While the copper tubes I2 are held in their lowered position shown in Fig. 1, the tube II is moved upwardly and the iron powder within said tube will flow out through the open end thereof and fill the central portion of the mold cavity inside of the circular row of tubes i2, and will also flow in between said tubes and around the outside thereof, thereby filling the entire space within the mold cavity except that which is occupied by the tubes i2.

Fig. 2 shows the tube II partially raised and illustrates the process of filling the cavity with the iron powder except for the space occupied by the tubes I2.

The tube H is raised to the position shown in Fig. 3, in which position nearly all of the measured quantity of iron powder has been delivered through said tube. The tube H is then held stationary in this position and the smaller tubes I2 are raised. A they rise the copper powder within them flows out through their lower ends and fills the spaces within the mass of iron powder which was formerly occupied by the tubes !2. Said tubes l2 are raised to a point above the lower end of the stationary tube II as shown in Fig. 3 with the result that a quantity of the copper powder will fill the annular space of the mold cavity surrounding the lower end of tube II as shown at I5, Fig. 3, and thereby a ring of copper powder is formed which eventually constitutes one of the end members of the completed rotor. The measured quantity of copper powder is such that by the time the ring I5 has been deposited all the copper powder in the tubes I2 has been delivered.

The tube I I is then raised still further and the remaining iron powder in the tube I I is deposited within the ring I5. The quantity of iron powder thu delivered is such that the mass of iron powder i6 within the ring i5 will have a dome shape or convexly upper surface as shown at W.

The die member 6 with the iron and copper powder thus deposited therein is then removed from the loading mechanism and an upper punch I9 is inserted in the upper end of the mold cavity,

said punch i9 having an axial opening to receive the shaft 8 and also having a recess 2! corresponding to the recess iii of the lower punch I.

Pressure is then applied to the two punches i and i9 tending to force them toward each other and thereby compressing the powdered iron and powdered copper within the mold cavity in order to form the rotor as shown in Fig. 5. The amount of pressure required for this purpose may vary somewhat but a pressure on the orderof fifty A tons per square inch will probably be sufficient. In filling the mold cavity the copper powder is delivered into the mass of iron powder in the form of columns 3a which are integral at one end with the lower ring i l of copper and are invtegral at their upper end with the ring it.

tered at an appropriate temperature, which may be on the order of 1850 F.

The rotor thus formed is molded to exact dimensions and it presents the iron core 5, the two end members 2 of copper, and the conductor bars 3 connecting the end members.

A suitable means for filling the tubes iI and I2 with the measured quantities of iron powder and copper powder and for raising the tubes to deliver the powder to the mold cavity as above described is illustrated in Fig. 1. Such means include a supporting frame having vertical members 22 which are secured to and rise from a base plate 23 adapted to rest on the die block b. Mounted for vertical movement of the frame is a head member Hi to which the upper end of the tube H is attached. In order to guide the member 24 in its vertical movement it is provided with ways 25 in which the vertical elements 22 of the frame are received.

Mounted on the head M is a hopper 25 adapted to contain the powdered iron ingredient of the rotor, and situated between the bottom 2? of the hopper and the head 24 is a measuring unit 28 which is provided with a plurality of measuring chambers 29 extending vertically therethrough. The measuring unit 28 is in the form of a disk and is turnable about its axis by means of a handle 30. The bottom 27 of the hopper has a plurality of discharge openings 3!, which are so situated relative to the measuring chambers 29 that when the measuring unit is in one position, as shown in Fig. 1, the chambers 25 are out of alignment with the discharge openings 3| of the hopper, as illustrated in Fig. 13, while when the measuring unit is turned to a different position the measuring chambers 29 are brought into registry with the discharge openings 3|.

The head 24 is provided with a plurality of delivery passages 33, one for each measuring chamber 29, all of which communicate with the upper end of the tube Ii and which are so located that when the measuring chambers are in registry with the discharge openings 3i of the hopper, said chamber will be out of registry with the delivery passages 33, while when the measuring unit is in its other position the delivery passages 33 will be in registry with measuring chambers 29.

When the measuring unit 28 is in loading position with the measuring chambers 29 communicating with the discharge openings (il in the hopper but out of communication with the discharge passages 33, the measuring chambers are filled with iron powder thereby loading the measuring unit with a measured quantity of iron powder. When the measuring unit is turned to bring the measuring chamber into registry with the discharge passages 33, the iron powder contained' in the measuring chambers is deposited into said passage and thence into the tube I I.

A similar measuring device is used for filling the smaller tubes I2, such device including a hopper I4 adapted to contain copper powder which is mounted on a base plate to which the upper ends of the tubes I2 are secured and which in turn is carried by a member 36 that is movable vertically in the frame 22. The base plate 35 has a block 31 mounted thereon which is provided with discharge passages 38, one for each of the tubes I2, each passage 38 communicating with the upper end of the corresponding tube. Situated between the block 31 and the bottom I8 of the hopper I4 is another measuring unit 39 which has a pluralityof measuring chambers 40, one for each of the delivery passages 38. The bottom I8 of the hopper I4 is also provided with a plurality of discharge openings 4I, one opening for each of the measuring chambers 40. The measuring unit 39 is in the form of a disk which is turnable about its axis, and the discharge openings M and measuring chambers 40 are so disposed that in one position of said measuring unit each discharge opening M is in registry with the corresponding measuring chamber 40 and all measuring chambers 43 are out of registry with the delivery passages 38, while when the measuring unit is turned into its other position the measuring chambers 40 are moved out of registry with the discharge openings 4| and into registry with the delivery passages 38.

In filling the tube I2, therefore, the measuring unit is turned into the position shown in Fig. 1 in which each measuring chamber 49 is in registry with its discharge opening 4| whereby all of the chambers 40 will be filled with copper powder. The measuring unit 39 is then turned to its other position to carry the filled measuring chambers out of registry with their discharge openings 4| and into registry with the various delivery passages 38, so that the measured quantity of copper powder in each measuring chamber 40 will be delivered through the corresponding passage 38 into the corresponding tube I2.

Any suitable means may be employed for raising the tubes II and I2 to effect the delivery of the iron and copper powder into the mold cavity. As herein shown, the head 24 has connected thereto two rods 42, one of which is connected to a flexible cord 43 and the other of which is connected to a flexible cord 44. These cords 43, 44 pass over direction pulleys 45 at the upper end of the frame 22 and are connected to a lever 46 pivoted to the frame at 41. By depressing the lever 46 the head 24 is raised thereby raising the tube I I and by this means the tube I I can be manipulated for depositing the iron powder into the mold cavity.

For raising the tubes I2 the plate 36 has connected thereto two rods 41, one of which is connected at its upper end to a flexible cord 48 and the other of which is connected to a flexible cord 49. These cords 48, 49 pass through openings 50 in the head 24, and also pass over direction pulleys 5| carried by the frame and are connected to a second lever 52 also pivoted to the frame at 41 so that by depressing the lever 52 the plate 36 which carries the hopper I4 is raised and thereby the tubes I2 are withdrawn from the mold cavity as above described.

The loading device herein shown is so made that the copper powder can be deposited in the mold cavity in a manner to produce a rotor having conductor bar which are parallel to the rotor axis, as illustrated in Figs. 5 and 9, or one in which said conductor bars have inclined positions as seen in Fig. '7, or one in which the conductor bars have an angular shape as seen in Fig. 8.

If during such withdrawing movement of the tubes I2, the plate 35 has no turning movement about said axis, then the copper powder delivered from the tubes will form conductor bars 3 which are parallel to the axis of the mold cavity and hence parallel to the axis of the rotor, as shown in Figs. 5 and 9, but if the plate 35 and the tubes I2 carried thereby are given a uniform turning movement about the axis of the mold cavity during such withdrawing movement, the column of copper powder delivered from each tube l2 will have an inclined position relative to the axis of the mold cavity, thereby producing a rotor having straight conductor bars which are inclined to the rotor axis as shown in Fig. 7.

The hopper I4, the measuring unit 39, the block 37, the plate 35 and the tubes I2 attached thereto, are so constructed and assembled that they constitute a unitary structure that can be turned as a unit about the axis of the mold cavity during the withdrawing movement of the tubes I2.

The skirt 54 of the hopper is secured to the block 3? by screws 55 and said block is secured to plate 35 by other screws 56. The plate 35 is provided on its under side with a central boss 57 which fits and is turnable in a circular recess E8 in the plate 36. The plate 35 has a projection 58 extending from its periphery which is adapted to engage a cam face 59 on a cam member 53; during the upward movement of said plate by which the tubes I2 are withdrawn from the mold cavity. Said cam member is shown as being secured to the frame 22, and if the cam face 59 is a straight face having a position inclined to the vertical, as shown in Fig. 16, the plate 35 carrying the tubes I2 will be given a uniform turning movement about the axis of the mold cavity during the withdrawing movement of the tubes, thereby producing the inclined conductor bars 30 shown in Fig. '7.

If the cam face has an angular shape as shown at 59a in Fig. 18 then the plate 35 and the tubes I2 will have a turning movement in one direction during the first part of the withdrawing movement and a turning movement in the opposite direction during the last part of such withdrawing movement, thereby producing a rotor with angular conductor bars 3b as shown in Fig. 8.

The projection 58 which engages the cam face 59 or 5911 is preferably acted on by a spring 6| which holds it in operative engagement with the cam face.

In Figs. 11 and 12 there is shown a rotor embodying my invention which has fan blades 62 at each end. These may be provided for by forming the faces of the punches I and I9 with properly shaped recesses which when the powder within the mold cavity is subjected to pressure to mold the rotor, form the desired fan blades.

I claim:

1. An apparatus for loading metal powder into the mold cavity of a mold preparatory to compressing the powder in said mold to form the rotor for an induction motor, said apparatus comprising a mold having a mold cavity, a delivery tube open at both ends extending axially into the mold cavity with its open lower end resting against the bottom of said cavity, a plurality of smaller delivery tubes also open at both ends and extending into said mold cavity and situated in a circle surrounding the axially located tube with the open lower ends thereof spaced from the bottom of the mold cavity, a measuring element above the axially located tube for measuring a predetermined quantity of iron powder and delivering it to said tube, a second measuring element for measuring a plurality of predetermined quantities of copper powder and delivering one such measured quantity to the upper end of each of the smaller tubes, means to withdraw the axially located tube from the mold cavity while the smaller tubes remain stationary, whereby the iron powder in said withdrawn tube is deposited in the mold cavity and encloses the smaller tubes, and means thereafter to withdraw from the mold cavity the smaller tubes whereby the copper powder therein is deposited therefrom through the lower open ends thereof into the spaces within the deposited iron powder which were previously occupied by said smaller tubes.

2. An apparatus as set forth in claim 1 in which means are provided to turn the smaller tubes as a unit about the axis of the mold cavity while they are being withdrawn.

3. An apparatus as set forth in claim 1 in which the smaller tubes are suspended at their upper ends from a plate mounted for turning movement about the axis of the mold cavity, and means are provided for turning said plate about said axis during the withdrawing movement of the tubes.

4. An apparatus for loading a mold comprising a hopper for containing powdered iron located above the mold and having a discharge opening in its bottom, a vertically movable head on which said hopper is mounted, a delivery tube suspended from said head and extending axially into the mold cavity, the lower end of the tube being open and resting on the bottom of said cavity, said head having a delivery passage communicating with the upper end of the tube, a measuring element situated between the bottom of the hopper and said head and having a measuring chamber, said measuring element being turnable between a position in which the measuring chamber is in registry with the discharge opening of the hopper and another position in which said measuring chamber registers with said dicharge passage in the head, whereby measured quantities of iron powder can be delivered from the hopper to the tube, a plurality of smaller tubes extending into said mold cavity and arranged in a circle surrounding the axially located tube, means to deliver a measured quantity of copper powder into each of said smaller tubes, means to withdraw from the mold cavity first the axially aligned tube thereby to deposit in the mold cavity the measured quantity of iron powder and means subsequently to withdraw from the mold cavity the smaller tubes whereby columns of copper powder are deposited in the mold cavity in the spaces previously occupied by said smaller tubes.

5. An apparatus as set forth in claim 4 having means to turn the smaller tubes as a unit about the axis of the mold cavity during the withdrawing movement of said tubes.

6. An apparatus for loading metal powder into a mold comprising a mold having a mold cavity, a hopper for containing iron powder also situated above the mold, a delivery tube open at its lower end extending axially into said mold cavity and having its open end resting on the bottom of said cavity, means for measuring a predetermined quantity of iron powder from the hopper and delivering said measured quantity into said delivery tube, a second hopper for containing copper powder, a plurality of smaller tubes extending into said mold cavity and situated in a circle surrounding and spaced from the axially located tube and with their open lower ends spaced from the bottom of the mold cavity, means to measure a plurality of equal quantities of copper powder from said second hopper and deliverone such measured quantity into each of said smaller tubes, means to withdraw the axially located tube from the mold cavity while the smaller tubes remain stationary, whereby the iron powder in said withdrawn tube is deposited in the mold cavity and encloses the smaller tubes, and means thereafter to withdraw the smaller tubes simultaneously from the mold cavity, thereby forming columns of powdered copper in the spaces previously occupied by the smaller tubes.

ETHAN CHARLES HOPKINS.

REFERENCES CITED The following references are oi record in the file of this patent:

UNITED STATES PATENTS Number Name Date 682,243 Cuscaden Sept. 10, 1901 l,171,579 Atterbury Feb. 15, 1916 2,244,367 Kinkead June 3, 1941 2,275,420 Clark Mar. 10, 1942 2,533,986 Atterbury Dec. 12, 1950 

